SwRI: Many famous comets formed in other solar systems

[bystander]

Many famous comets originally formed in other solar systems
Southwest Research Institute (SwRI) - 10 June 2010
Queen's University - 10 June 2010

Many of the most well known comets, including Halley, Hale-Bopp and, most recently, McNaught, may have been born in orbit around other stars, according to a new theory by an international team of astronomers led by a scientist from the Southwest Research Institute (SwRI) in Boulder, Colo.

Dr. Hal Levison (SwRI), Dr. Martin Duncan (Queen's University, Kingston, Canada), Dr. Ramon Brasser (Observatoire de la Côte d'Azur, France) and Dr. David Kaufmann (SwRI) used computer simulations to show that the Sun may have captured small icy bodies from its sibling stars while it was in its birth star cluster, thereby creating a reservoir for observed comets.

While the Sun currently has no companion stars, it is believed to have formed in a cluster containing hundreds of closely packed stars that were embedded in a dense cloud of gas. During this time, each star formed a large number of small icy bodies (comets) in a disk from which planets formed. Most of these comets were gravitationally slung out of these prenatal planetary systems by the newly forming giant planets, becoming tiny, free-floating members of the cluster.

The Sun's cluster came to a violent end, however, when its gas was blown out by the hottest young stars. These new models show that the Sun then gravitationally captured a large cloud of comets as the cluster dispersed.

The Sun as comet snatcher
Nature News - 10 June 2010

New simulations suggest that the Sun may have captured more than its fair share of comets from the primordial star-forming soup. The study, led by Harold Levison of the Southwest Research Institute in Boulder, Colorado, seeks to account for the abundance of comets in the outer reaches of the Solar System.

Our Solar System's comets spend most of their time between roughly 5,000 and 100,000 times further away from the Sun than the Earth, in a little-understood region beyond the planets known as the Oort cloud. Occasionally, some zip past the inner Solar System, and a rare few, such as Halley's Comet, return on a regular basis. But the origin of even the most well known comets is something of a mystery.

An influential model of how the Solar System formed predicts that around 6 billion comets in the Oort cloud are home-grown¹. But some astronomers estimate that there are as many as 400 billion comets surrounding the Solar System — a discrepancy that researchers have struggled to explain.

Now the Levison study suggests that these mystery comets may actually have formed around other stars during the first moments of star formation. "Our Sun is a relatively heavy star," explains Ramon Brasser, a co-author of the study, which appears online in Science today². When material such as gas, dust and ice began to find gravitational dancing partners, our Sun may have been massive enough to skim spare comets from its more lightweight neighbours.

1. From the Kuiper Belt to Jupiter-Family Comets: The Spatial Distribution of Ecliptic Comets
   • Icarus, Volume 127, Issue 1, Pages 13-32 (May 1997), doi: 10.1006/icar.1996.5637
2. Capture of the Sun's Oort Cloud from Stars in Its Birth Cluster
   • ScienceXpress, 10 June 2010, DOI: 10.1126/science.1187535

Many Famous Comets May be Visitors from Other Solar Systems
Universe Today - 10 June 2010

Halley's Comet and Others May be Stolen Goods
Space.com - 10 June 2010

Many Solar System Comets May Have Been Swiped from Other Stars
Scientific Americn - 10 June 2010

[neufer]

http://asterisk.apod.com/vie ... 13#p122477

[bystander]

Familiar comets may have distant roots
Science News - 10 June 2010

Other stars may have given birth to majority of objects in the solar system's far-out cloud of icy debris

When it comes to adoption, the sun may have it all over celeb parent Angelina Jolie. Most of the hundreds of billions of small fry in the outermost reaches of the solar system — comets in a vast reservoir called the Oort cloud — might have been born around other stars and only later moved to the sun, new computer simulations suggest.

If the findings are correct, the sun may have adopted such familiar comets as Halley, Hale-Bopp and Kohoutek from other stars. These comets are émigrés from the Oort cloud that have visited the inner solar system.
...
Other researchers, while noting that the study is intriguing and carefully done, say they have qualms about the results because so little is known about the early history of the sun and about the Oort cloud’s current population. Responding to the study team’s assertion that more than 90 percent of Oort cloud comets were born around other stars, “I would answer ‘hold your horses,’ because I don't think anything has been proven yet,” says planetary scientist Hans Rickman of the Uppsala Astronomical Observatory in Sweden, who was not involved in the study.

• 
  Free-floating comets (green and blue dots) move randomly within a young cluster of stars
  (orange and red) at the beginning of this computer simulation. When supernova explosions
  and strong stellar winds break apart the cluster, the comets (blue) traveling in the same
  direction as the red star become members of that star's Oort cloud. Courtesy of H. Levison

• 
  Two nearby stars of different sizes (red dots) have a gravitational encounter. The larger
  star grabs comets (blue) from the smaller star, creating an Oort cloud. Courtesy of H. Levison

[Beyond]

Hey.......just like on Earth -- to the victor belong the spoils.